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I know that there have been 318 vs 325 posts before, but I think I'm asking different questions.

Here I go:

Basically I really want to get into autocrossing but at the same rate I want to N/A tune my engine because I know that I will learn a lot about engine trends by doing this.

I've sort of "chosen" the E30 325is or 318iS as possible platforms for which to do this...

I want to ask everyone if they've seen any aggressively N/A tuned 318's or 325's with the stock block (meaning without an engine swap). These cars will normally have aggressively-tuned valvetrains as well as changes to bottom-end parts. This is what I want to do, heh.

If anyone's seen racing applications for E30 318's or 325's and would you be able to point me towards dyno charts proving this, it'd be much appreciated. I'm trying to decide whether the SOHC 4-cylinder or SOHC 6-cylinder will be better for my purposes.

If learning is your main goal, then using an M20 in a 325i/is would be perfect. It is a relatively simple engine to work on, and offers great power and torque right out the box.

That said, if you want power to be made, I'd rather buy a 318is and swap in an M50 from an E36. The engine has a lot more potential, most notably the 4-valve head design. The M20 is handicapped by it's ancient head design.

Then again, if you do the M50-318is route, you'd even learn about hybrids too.

By the way, I thought the 318iS used the M40 or M42 or something (I think I misspoke by saying 4-cylinder SOHC instead of saying DOHC)

Thanks for the quick responses so far!

I want a really unrefined car; not just in creature comforts but also in the fact that it doesn't run out of breath at a low rpm. Ideally, I'd like to have a very high-revving engine. And, I do anticipate modifying the valvetrain heavily as I know this will be required. I'm not looking to get HUGE amounts of power but I don't think 250-300hp is out of range. I know there's a limit to what I want, but swapping really isn't something that I want to do (not because of difficulty just because it sounds more fun to me to use the block that came with the engine).